Compound cavity reflection modulation laser system

Abstract

The invention relates to compound cavity optical reflection modulation laser system providing frequency modulation of laser light by phase induced effective reflection modulation of the laser rear facet. The system includes a single mode gain coupled DFB laser integrated with a passive waveguide section to form a compound cavity modulation system. The waveguide includes a multiple quantum well region which is reverse biased to utilize the quantum Stark effect for voltage controlled refractive index modulation, thus providing phase modulation of the laser light. The phase modulated light is fed back to the laser to interfere with the light generated within the laser and to form the output light generated from the compound cavity. The interference effects cause modulation of the effective complex reflection of the rear laser facet which results in frequency modulation of the output light. If required, the frequency modulated light (FM) may be converted into intensity modulated (IM) light by using an additional narrow band optical filter, e.g. Mach-Zehnder interferometer.

What is claimed is:  
     
       1. A compound cavity reflection modulation laser system for providing frequency modulation of output light generated therein, comprising: 
       a first cavity forming a single wavelength semiconductor laser between a front laser facet and a rear laser facet, said first cavity producing interference effects of a received phase modulated light to provide modulation of the complex reflection of said rear laser facet;  
       means for converting frequency modulation (FM) into intensity modulation (IM), said means being situated to receive output from said front facet of said laser; and  
       a second cavity forming a phase modulation element between a front element facet and a rear element facet, said second cavity receiving light generated by said first cavity to provide said phase modulated light, said first and second cavities forming a compound cavity defined by said front laser facet and said rear element facet, wherein the modulation of said complex reflection of said rear laser facet provide frequency modulation of said output light.  
     
     
       2. A system as defined in  claim 1 , wherein the laser and the phase modulation element are monolithically integrated on the same chip. 
     
     
       3. A system as defined in  claim 1 , wherein the laser and the phase modulation element are hybrid integrated into the system. 
     
     
       4. A system as defined in  claim 1 , wherein the laser is a DFB laser. 
     
     
       5. A system as defined in  claim 4 , wherein the DFB laser is one of a gain-coupled laser and a loss-coupled laser. 
     
     
       6. A system as defined in  claim 1 , wherein each of the front element facet and the rear element facet is one of a cleaved facet and a high reflection coated facet. 
     
     
       7. A system as defined in  claim 1 , wherein each of the front element facet of the phase modulation element and the rear facet of the laser is one of an anti-reflection coated facet and a cleaved facet. 
     
     
       8. A system as defined in  claim 1 , wherein the means for FM to IM conversion comprises a Mach-Zehnder interferometer. 
     
     
       9. A system defined in  claim 8 , wherein the Mach-Zehnder interferometer is a fiber interferometer.